This invention relates to an incandescent lamp for use in a reflector, and, more particularly, to an incandescent lamp to be fixed in a focused position in the reflector.
Incandescent lamps used in automotive reflectors are fixed in the reflectors as replaceable lamp assemblies in such a way that the reflector and the lamp form a closed unit in which a sealing rubber prevents humidity or dust from penetrating into the reflector. The incandescent lamp is equipped with locking elements constituting detachable joints with the elements formed in the wall of the reflector. The envelope of the incandescent lamp is set inside the reflector, while the terminals providing connection to the electrical circuit of the automobile are set outside of the reflector. The incandescent lamp must be fixed in the reflector so that the filament of the incandescent lamp takes a precisely defined position in the reflector-envelope otherwise the beam would deviate from the applicable standards. The incandescent lamp must keep this optical position during the operation, that is impacts and vibrations of the automobile must not dislocate the lamp from its position described above. At the same time, the fixing must be detachable so that the incandescent lamp can be replaced in the event of its defect. According to the effective IEC Standard No. 60061-2, the fixing is accomplished with a springy locking element pressing the incandescent lamp into the so-called V-supports shaped in the wall of the reflector by at least 10 N force. The locking element is simultaneously wedged in an indent shaped in the wall of the reflector.
A vehicle headlamp system is described in U.S. Pat. No. 5,855,430 comprising an optical reflector and an incandescent lamp. The optical reflector has an optical surface, which faces a forward direction, and a wall defining an opening formed therethrough. The reflector wall includes an axial positioning surface and a planar positioning surface. The lamp includes a light source with an envelope and a pinched portion, a sleeved optical disc having a metal support sleeve and a metal support portion. The metal support portion couples with the light source adjacent the pinched portion. A plastic bass, fixedly holds the sleeved optical disc, and has passages formed to pass the electric lead-outs through the plastic base to couple with terminals held by the plastic base, too. The headlamp system additionally includes a spring positioned to act between the internal reflector wall and the lamp so as to press between the reflector and the lamp in a direction orthogonal to the lamp axis. The spring comprises a resilient section of curved metal between two feet located in a cavity formed in the lamp. The feet act as guides to retain and direct the action of the spring. When the inner foot is properly positioned, the outer foot can slide in the cavity by the spring force and thereby apply pressure through its contact face that can slide and press on the internal reflector wall. Fixing the lamp in the opening of the reflector wall with rotation, the spring is compressed by advancing against the interior reflector wall, and the side of a ramp formed on the inner side of the reflector wall, thereby exerting in a direction perpendicular to the axis of the lamp.
Another incandescent lamp applicable in automotive reflectors is described in U.S. Pat. No. 5,957,569. This lamp has a plastic base, a metal support portion and a metal support sleeve, too. The lower part of the metal support portion is attached to the metal support sleeve while its upper part is fixing the envelope of the incandescent lamp. The lower part of the metal support sleeve is embedded in the plastic base and the upper part of the sleeve is equipped with optical flanges. The filament of the lamp is connected through lead-out wires to terminals which can be connected to the electrical circuit of the automobile. The incandescent lamp is fixed in the reflector by placing the lamp in the opening at the rear end of the reflector, while the optical flanges penetrate into the grooves shaped in the opening of the reflector and designed to match these optical flanges. Then the lamp is twisted around its longitudinal axis while the incandescent lamp is fixed in the reflector. Fixing is provided for by a compression spring which, in one of the embodiments, is welded to the outer wall of the metal support sleeve with one end, while the other end is resting free on the outer wall of the metal support sleeve. The middle of the compression spring constitutes a flare resting on the rim of the opening of the reflector when the lamp is twisted in the reflector.
In an other embodiment, the compression spring is designed as a flaring leafspring, but its ends are placed into the apertures between the metal support sleeve and the plastic base. The flaring portion of the leaf-spring protrudes outside of the outer wall of the metal support sleeve. When the flaring portion of the leaf-spring is compressed in the course of fixing the incandescent lamp in the reflector, the ends of the leaf-spring slide deeper into the apertures, while the. flaring part abuts along the opening of the reflector as described above.
In a further configuration, the flaring leaf-spring protrudes through a breach formed in the wall of the metal support sleeve under one of the three optical flanges. The ends of the leaf-spring rest on the bumpers designed on the metal support sleeve and the plastic base so that the leaf spring is compressed between these two bumpers also designed as supports.
In all the above cases, the compression spring is made from spring steel, which must be bent to provide the required shape, and it reaches the final shape when the lamp is fixed in the reflector. Since the length of the spring is relatively short, the stress occurring within the metal is relatively high. Metal s made of steel and capable of providing sufficient spring force has to be resilient in order to avoid irreversible distortion. During the compression of a spring, the stress in the metal must not exceed the elastic limit and come to overstrain. The stress in the metal depends on the geometry and the quality of the material. In one hand, there are steel materials with excellent spring characteristics but their stain resistance is not suitable for use in an automotive lamp. In the other hand, there is spatial limitation for the geometry of a spring in an automotive lamp. This limitation refers to the length of the spring which, despite the restricted room in the lamp inside, has to be long enough in order to present sufficient elasticity. Springs applied in the above cases have relatively short lengths thus the stress in the springs are close to the elastic limit.
Thus there is a particular need for an incandescent lamp, preferably for an automotive lamp, the leaf-spring of which used for fixing in a reflector is stainless however has a good springing, and can be manufactured and mounted into the lamp easily.
In an exemplary the embodiment of the invention, an incandescent lamp for use in a reflector is provided. The incandescent lamp comprises an envelope with a longitudinal axis, at least one filament and electrical lead-out wires. The lamp has a support portion receiving the envelop and a sleeved optical disc associated operatively with the support portion. The sleeved optical disc has a cut-out in a mantle thereof. A plastic base belongs to the incandescent lamp anchoring the sleeved optical disc and includes terminals. A leaf-spring is bent substantially to an O-shape and located in a space defined by the mantle of the sleeved optical disc. The leaf-spring includes a tongue protruding from one portion of the O-shape. The leaf-spring has two end portions forming a tab protruding from another portion of the O-shape. The leaf-spring is pressed to an inner portion of the mantle of the sleeved optical disc at the tab so that the tongue extends through the cut-out in the mantle of the sleeved optical disc.
An incandescent lamp in combination with a reflector is also provided, where the tongue is engaged in an indent formed in an opening of a wall of the reflector after the incandescent lamp is fixed therein.
The advantage of the present invention over both prior art patents quoted above is that the use of a lengthened leaf-spring bent to an O-shape requires less stress in the material of the spring even if it is pre-pressed when -mounted in the lamp. Owing to the less stress arising in the spring, a more suitable spring material can be selected with due regard to stain resistance. Moreover, the spring can be manufactured and mounted in the lamp easily.